Repturable opening for sealed container

ABSTRACT

A container formed from a paperboard laminate and including a rupturable opening for gaining access to the contents of the container, the opening being defined by an embossment pattern in a wall of the container. The embossment defines a weakened area which includes the layers of the laminate, but without destruction or deterioration of selected ones of the barrier/sealing layers of the laminate. A method is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

FIELD OF INVENTION

This invention relates to rupturable openings useful for gaining accessto the contents of a closed (sealed) container and methods for formingthe same.

BACKGROUND OF INVENTION

Liquid comestibles, commonly are offered to the consumer containedwithin closed (sealed) containers formed from laminates which include apaperboard substrate having at least one or more outer barrier layers.Such barrier layers insulate the paperboard from access to moistureoriginating either internally or externally of the container. At times,the barrier layer(s) further bar or reduce the transfer of gas throughthe container wall. The outer layer, at times, may comprise a heatsealing layer, which may also serve a barrier function.

Access to the contents of the container are commonly afforded byinserting a common drinking straw through an opening defined in the wallof the top end of the container. Such areas have heretofore taken manyforms, such as multiple slits radiating from a central point andextending partially or fully through a wall of the container, partialperforations through the container wall, or other techniques. Mostcommonly, such areas are defined employing cuts partially through thethickness of the container wall, thereby permitting the rupture of thearea using a common drinking straw, for example, to thereby gain accessto the interior of the container. Also, the prior art includes thetechnique of providing slits or cuts through most or all of thethickness of the wall of the container, with these slits or cuts beingtemporarily sealed with a removable patch, cover, or a flap of thecontainer.

It is noted that in the industry there exists containers for comestiblessuch as milk for example, wherein the container is of a lidded cupgeometry. However, in certain of these containers, the opening forgaining access to the contents of the container is located at the bottomof the container, i.e., at that end of the container opposite the lid.In the present disclosure, the term “top wall” of the container is to beconstrued as referring to that wall of the container through whichaccess to the contents of the container is achieved employing an openingas disclosed herein. Thus, in the aforedescribed lidded cup, the “topwall” of such container would include the actual bottom wall of the cup.

These prior art techniques for weakening the container wall forinsertion of a drinking straw, for example, suffer from variousproblems. Obviously, unsealed full cuts through the thickness of thecontainer wall are impermissible. Weakening an area of the containerwall by cutting partially through the thickness of the wall requiresprecise cutting of the blank from which the container is ultimatelyformed. Known commercial production equipment used for this purpose hasbeen found unreliable for producing such partial thickness cuts. Suchunreliability is exacerbated by variances in the thickness of thelaminate being cut as well as other factors.

Attempts have been made in the prior art to produce weakened areas inthe container wall by embossing a pattern in the container wall. Incertain containers formed from paperboard laminates and intended tocontain a liquid, it is permissible that one or more, but less than all,of the layers of the laminate to be ruptured in the course of definingan opening to be used for future access to the contents of thecontainer. This is true, for example, with containers for liquids havinga short shelf life, such as milk. With containers for other liquids suchas orange juice, it is impermissible that the liquid in the container beallowed access to the fibers of the paperboard substrate of thelaminate. Known embossing patterns and their techniques of productionhave been found to rupture the outer layers of barrier or sealingmaterials that are laminated to one or both of the opposite surfaces ofa paperboard substrate, thereby exposing the absorbent fibers of thepaperboard to soak up liquid from inside the container, or to soak upliquid from the exterior of the container, either such event destroyingthe ability of the laminate to contain the contents of the containerwithin the container, or permitting inadvertent puncture of the weakenedarea of the container wall. In more severe instances, leakage of thecontainer contents results, while in any such instance, the purity,flavor, etc. of the container contents may be compromised. Whereas, asnoted, rupture of one or more of the barrier or sealing layers of apaperboard laminate to be used to form containers for liquids, ispermissible in certain containers, such layer rupture is not permissiblein other containers for liquids. Known prior art techniques, includingknown embossment patterns, have been found to be lacking in theirability to consistently provide a weakened area in a wall of a containerfor liquids employing a paperboard laminate, wherein the weakened arearemains intact to the extent necessary to retain the contents within thecontainer and/or to protect the contents of the container againstundesired alterations of the contents of the container, and still isreadily rupturable by a common drinking straw.

SUMMARY OF INVENTION

In accordance with the present invention, there is provided an improvedrupturable area in the wall of a container for selectively gainingaccess to the contents of the container, such improvement including apattern of at least first and second elongated (e.g., linear)embossments which intersect one another, such as at approximately theirrespective midpoints. Each embossment is of substantially semi-circular,e.g. rounded, cross-sectional geometry whereby the area immediatelyadjacent their intersection is substantially less resistant to ruptureupon the application of a rupturing force in the nature of a drinkingstraw urged against the intersection of the embossments, than in thoseareas of the embossments disposed laterally outwardly of theintersection of the embossments.

The present invention is particularly useful for providing selectiveaccess to the contents of a container formed from a paperboard substratewhich has a barrier or sealing outer layer of polymeric material bondedto one or both of the outer surfaces of the paperboard. In this latterembodiment, the embossment is performed on a blank from which thecontainer is to be formed. Preferably, the embossment projects outwardlyof the outer surface of the wall of the finished container, but theembossing may be performed from either of the outer surfaces of thecontainer blank, as desired.

In the method of the present invention, a blank intended to be erectedinto a container is embossed in accordance with the present inventionemploying male and female mating dies, the male die preferably beingdisposed on that surface of the blank which will ultimately become theinner wall of the erected container. Through the choice of the extent ofclosure between the male and female dies, with the laminate paperboarddisposed therebetween, and the size and geometry of the projection onthe male die and the cavity in the female die, the present methodrepetitively provides uniform embossment with consistent rupture of lessthan all the layers of the laminate paperboard or as desired,non-rupture of any of the layers of the laminate, or of one or morelayers of the laminate other than at lease one layer which is designedto be a barrier against ingress or egress of gases or liquids into orfrom the container, or as a heat sealing layer useful in the forming ofthe container from a blank. The resultant embossment is readily rupturedusing a common drinking straw.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a laid out view of one embodiment of a blank useful forforming a container having a rupturable area defined in the top wallthereof according to the present invention;

FIG. 2 is a top view of one embodiment of an embossment pattern of thepresent invention;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2, of aportion of the top wall of a container and including an embossmentpattern embodying various aspects of the present invention plus adepiction of a drinking straw poised for rupture of the depictedembossment;

FIG. 4 is a side elevation view of a portion of a container wall asdepicted in FIG. 3 and schematically depicting the penetration of thewall with a drinking straw via a rupturable opening in the wallemploying various aspects of the present invention.

FIG. 5 is a perspective view of an embossment in a container wall andembodying various features of the present invention;

FIG. 6 is a representation of an alternative embossment patternembodying various of the features of the present invention;

FIG. 7 is a representation of an alternative embossment patternembodying various of the features of the present invention;

FIG. 8 is a representation of an alternative embossment patternembodying various of the features of the present invention;

FIG. 9 is a representation of an alternative embossment patternembodying various of the features of the present invention;

FIG. 10 is a representation of an alternative embossment patternembodying various of the features of the present invention;

FIG. 11 is a representation of an alternative embossment patternembodying various of the features of the present invention;

FIG. 12 is a side elevational view, in section, of a typical dieemployed in the formation of an embossment of the present invention;

FIG. 13 is a cross-sectional view of a portion of a laminate paperboarduseful in the present invention;

FIG. 14 is a cross-sectional view of a portion of a further laminatepaperboard useful in the present invention; and

FIG. 15 is a schematic representation of one embodiment of apparatus forembossing a laminate in accordance with the present invention.

DETAILED DESCRIPTION OF INVENTION

The present invention relates to a container particularly useful forcontaining a liquid comestible which is intended to be accessed andwithdrawn from the interior of the container via a common drinking strawwhich is also employed to rupture a relatively small weakened area in awall (usually the top wall) of the container and thereby permit thepassage of the straw into the interior of the container, all as is wellknown in the prior art and need not be described in detail.

FIGS. 3 and 4 depict a portion 20 of the top wall 22 of a container andthe entry of the end 24 of a straw 26 into the interior of the containervia a weakened area 38 in the wall of the container, the weakened areabeing ruptured using the end of the straw.

In one embodiment of the present invention, the paperboard laminate 10(FIGS. 13 and 14) comprises a paperboard substrate 12 having a thicknessof between about 15 and about 17 mils for example. In a typicalpaperboard laminate as used in the formation of containers for liquids,at least one, and commonly both, of the opposite surfaces 14, 16 of thepaperboard has bonded thereto a barrier layer 18, 19, commonly of apolymeric material, such as polyethylene which also may serve as abarrier against the entry into, or passage through, the wall of thecontainer of gas(es) or liquid(s) and/or as a sealant in the formationof the blank into a container. This barrier or sealing layer commonlymay be about 25 microns thick, for example. Whereas the laminatesdepicted in FIGS. 11 and 12 include only two and three layers,respectively, it will be recognized that the laminate may includeadditional layers, as desired or needed for a particular application ofthe laminate.

FIG. 1 depicts a typical blank 30 employed in the formation of a commongable top container which includes. one embodiment of an embossmentpattern 28 defined in one panel 32 of the top end 34 of the blank whichultimately becomes the top end of a container. The depicted blankincludes various fold lines 36, for example, commonly formed as scorelines into the thickness of the blank.

Referring to FIGS. 2-5, in accordance with one aspect of the presentinvention, a wall 22 of a container for a liquid comestible, forexample, is provided with a structurally weakened area 38 designed to beruptured using a common drinking straw 26. In the present invention thisweakened area takes the form of an embossment 40 defined in the wall ofthe container and which includes at least first and second generallyelongated (e.g., linear) portions 42 and 44, respectively, whichintersect 46 one another, for example, at their approximate midpoints.In the depicted, and, preferred, embossment, each of the linear portionsof the embossment is of a substantially semi-circular cross-section asseen in FIGS. 3, 5, 13, and 14. As a consequence of their formation byembossing, each of the linear sections is weakened to a first degree andsubject to ready rupture. Of importance in the present invention,through the use of such intersecting linear, semi-circularcross-sectional, portions 42, 44 of the embossment, the present inventorprovides an area within the intersection 46 of the linear portions whichis weakened to a second degree which provides lesser resistance torupture than the resistance to rupture of the remainder of each of thelinear portions of the embossment. Thus, the present embossment patternprovides an area within the embossment pattern which is readily rupturedby applying a force thereagainst using the end of a common drinkingstraw to provide ready and easy initial commencement of a rupture of theweakened intersection of the generally linear embossments. Once arupture of the weaker intersection area has commenced, less force isrequired to extend the rupture laterally of the intersection area intothose regions of the linear portions which emanate from the intersectionarea of the embossment pattern. The resultant displacement of rupturedportions 52, 54 of the embossment pattern after a straw has beeninserted into the interior of the container is depicted in FIG. 4.

In accordance with one aspect of the present invention, the pattern ofembossment is chosen to include at least first and second generallylinear portions 42, 44 which mutually intersect, preferentially bisect,one another. It is anticipated, however, that more than two linearportions may be employed, but are not required. Preferably, the linearportions are each of equal length, but different lengths of linearportions may be employed, including, for example, alternating lengths.In the embodiment depicted in FIG. 2, the terminal ends 56, 58 of thefirst linear position 42, and 60, 62 of the second linear portion 44 areeach tapered down and/or rounded, to decrease the likelihood of anyrupture of the weakened area extending beyond the terminus of eachlinear portion. In a typical embodiment, the centerline 64 of eachlinear portion of an embossment intersects, and preferably bisects, thecenterline 66 of each other linear portion of the embossment pattern. Inthe embodiment of FIG. 2, the termini of the two linear portions liewithin an imaginary circle 68 which is concentric with the point ofintersection 46 of the linear portions. In any event, the diameter ofthe imaginary circle (FIG. 2) exceeds the diameter of the straw to beused in rupturing the weakened area, but does not exceed such minimumdiameter to the extent that liquid will readily leak from the containerwhen the straw is inserted into the interior of the container. In atypical container, the diameter of the imaginary circle will rangebetween about 0.4 and about 0.6 inch in diameter. Further, whereas it ispreferred that each of the linear portions of the embossment be of thesame geometry, including the same width, it will be recognized thatcombinations of linear portions of differing widths may be employed.Examples of differing arrangements of linear portions 78-88 of theembossments 70-79, respectively, are depicted in FIGS. 5-11.

As seen in FIGS. 3, 5, 13, and 14, each linear portion of the embossmentof the present invention is of a semi-circular cross-section. In atypical embodiment employing a paperboard laminate of 16 mils thickness,the width “W₁” of each linear portion is chosen to be about 0.039 inch.Likewise, the height “H₁” of each linear portion is chosen to be about0.006 inch. In this example, the area of the weakened portion(intersection) of the embossment pattern is about 0.002 in². In thisembodiment, a rupture force. of about 4.7 lbf (mean value) applied tothe weakened area, using a 4 mm diameter drinking straw readily rupturedthe embossment.

Referring to FIG. 5 in particular, it will be seen that the intersection48 of the multiple linear portions 42, 44 of the embossment patternproduces an area 38 within and preferably about the center of thepattern the pattern which is a combination of the widths of theindividual ones of the linear portions. This structure defines a type ofweak bridge 90 (see FIGS. 13 and 14) over the intersection whichcomprises stressed, but integral, paperboard laminate. The presentinventors have found that this enlarged and weakened area offers lessresistance to rupture than the remainder of each of the linear portionsof the embossment. Thus, when the end of a common drinking straw isforced against such enlarged area 38, there occurs immediate and readyinitial rupture of the enlarged area. This rupture is readily spreadlaterally from the enlarged area along each of the linear portions tocreate an opening sufficient for the entry of the end of the straw fullyinto the interior of the container for the withdrawal of the containercontents via suction applied to the opposite end of the straw.

Importantly, in the present invention, each pattern of embossment isimparted to a blank 30 prior to erection of the blank into a container.To this end, the present inventor has found that formation of thedesired embossment of semi-circular cross-section preferably is formedemploying a male and female die set. A cross-sectional view of onesuitable die set 92 is depicted in FIGS. 12 and 15. In this die set, thefemale die 94 is provided with a cavity 96 of truncated pyramidalcross-section which is adapted to receive therein a portion of thelaminate paperboard blank which is forced into the cavity by a matchingprojection 100 of truncated pyramidal cross-section of the male die 102.In one embodiment, the height h, of the projection is about 60% greaterthan the depth of the female die cavity. Further, the width of the baseof the projection of the male die is about 57% greater than the width ofthe mouth of the cavity in the female die. These dimensionalrelationships provide substantially uniformly distributed pressureapplied to the paperboard laminate interposed between the male andfemale dies, hence uniform displacement of laminate paperboard andformation of an embossment pattern whose components are each of uniformthickness. Further, these dimensional relationships, employing a femaledie cavity and a male projection of truncated pyramidal cross-sectionform an embossment of substantially semi-circular cross-section. In apreferred embodiment, each embossment preferably does not extend abovethe plane of an outer (or inner as the case may be) surface of thelaminate paperboard by a distance greater than the approximate thicknessof the laminate paperboard. The final height of the embossed portion ofthe laminate paperboard is chosen by limitation of the extent of closingof the die set, a function which is readily accomplished and which hasbeen found to provide the uniformity of displacement of the paperboardlaminate out of its sheet form and into the embossment. Male and femaledies are readily incorporated into existing container blank-formingmachines, and are relatively inexpensive, so that their use in thepresent invention represents relatively little added cost to theproduction of container blanks. More importantly, the use of male andfemale dies provides that control over the uniformity of displacement ofthe paperboard laminate during formation of the embossment which isnecessary for automated production of container blanks. Still further,employing dies which define embossments of semi-circular cross-sectionhas been found to provide an unanticipated benefit relative to theability to selectively control the extent or degree of destruction ofthe outer polymeric layer(s) of the laminate paperboard, hence theabsence of spoilage, contamination, etc. of the contents of a containerhaving a rupturable area in accordance with the present invention. Stillfurther, such retained integrity of the outer layers of the laminatepaperboard precludes the leakage of liquid, either from exteriorly orinteriorly of the container, from being absorbed by exposed fibers ofthe paperboard itself, and resultant potential failure of the strengthof the container, among other things. Notably, the present inventorshave found that embossing the paperboard laminate between male andfemale dies having a truncated pyramidal female die cavity and acomplimentary geometry male die projection, squeezes the laminatetherebetween in a manner which provides the desired substantiallysemi-circular cross-sectional geometry of the embossment without ruptureof any outer layer of the laminate, or with limited rupture of one ormore, but not all, the layers of the laminate.

In accordance with one aspect of the present invention, with referenceto the apparatus schematically depicted in FIG. 15, there is provided amethod for the formation of a rupturable area in the wall of a blankfrom which a container may be formed comprising the steps of disposing aportion of a laminate paperboard 10 having an outer layer of barrier orsealing material on at least one surface thereof, as depicted in FIGS.13 and 14, between male and female dies 94 and 102, respectively, havingrespective projection 100 and cavity 96 features adapted to define anembossment of substantially semi-circular cross-section, and pressingsaid male and female dies together to that extent which defines saidembossment, but which does not destroy or otherwise damage the integrityof said outer layer of barrier material or other layers of the laminate.In the apparatus depicted in FIG. 15, the male and female dies aremounted on. the outer circumference of nip rolls 104 and 106,respectively, thereby providing for the embossment of succeeding blanksdefined on a sheet of laminate paperboard which is continuously fedthrough the nip rolls.

In the preferred method, the laminate material of the container wall isembossed from the inside outwardly of the container. That is, theembossment projects from the outer surface of the container, as opposedto the embossment projecting inwardly of the container. This feature ofthe invention provides for cleaner rupturing of the weakenedintersection of the rupturable area, followed by uniform spread of therupture along the individual linear portions of the embossment. However,as desired, the embossment may be formed from outside inwardly of thecontainer.

Whereas the present invention has been described using specific. valuesand terms, it is anticipated that one skilled in the art will recognizeacceptable alternatives or modifications of the invention and it isintended that the invention be limited only as set forth in the claimsappended hereto.

1. In a container formed from a laminate having a paperboard layer and alayer serving as a barrier layer, or as a sealing layer, or as both abarrier and sealing layer material on at least one of the oppositesurfaces of the paperboard layer, the container having a top end, theimprovement comprising a structurally weakened area defined inassociation with a wall of the container, said weakened area beingdefined by at least first and second generally elongated embossmentswhich intersect one another, each of said embossments having a curvedtransverse cross-sectional geometry which includes each of the layers ofthe laminate intact, and defining a weakened area for rupture thereofupon the application of a rupturing force in the nature of a drinkingstraw urged against said weakened area in the approximate location ofthe intersection of said at least first and second generally elongatedembossments.
 2. The improvement of claim 1 wherein said cross-sectionalgeometry of each of said at least first and second intersectingembossments is substantially constant in geometry over itscross-sectional area.
 3. The improvement of claim 2 wherein saidintersection of said at least first and second elongated embossmentsdefines an area of weakened resistance to rupture of said laminate atsaid intersection which is substantially less than the resistance torupture of either of said at least first and second embossments atlocations laterally displaced from said intersection thereof.
 4. Theimprovement of claim 1 wherein each of said embossments projectsoutwardly of said container and beyond the plane of an outer surface ofsaid laminate.
 5. The improvement of claim 4 wherein each of saidembossments projects beyond the plane of an outer surface of saidlaminate by a distance not greater than about the wall thickness of thecontainer.
 6. The improvement of claim 1 wherein said laminate includesa layer of polyethylene on each of the opposite surfaces of saidlaminate.
 7. The improvement of claim 6 wherein said embossments do notdestroy the continuity of said polyethylene layers on said laminate. 8.The improvement of claim 1 wherein said embossments are substantiallylinear.
 9. The improvement of claim 1 wherein all layers of the laminateremain functionally intact.
 10. The improvement of claim 1 wherein saidat least first and second embossments structurally weaken said laminatein the area of said embossments.
 11. The improvement of claim 1 whereinsaid weakened area exhibits a resistance to rupture of about 4.7 lbfapplied to said weakened area by a drinking straw of about 4 mmdiameter.
 12. The improvement of claim 11 wherein said straw is of apolymeric material.
 13. A method for enhancing access to the liquidcontents of a closed container formed from a paperboard laminate andhaving a top wall comprising the steps of providing a pattern ofembossments in a top wall of the container said pattern including atleast first and second elongated embossments which intersect one anotherat least once along their respective lengths, each of said elongatedembossments having a curved substantially semi-circular cross-sectionalgeometry, the locus of intersection of said embodiments defines astructurally weakened area having a lesser resistance to rupture thanthe remainder of said elongated embossments.
 14. The method of claim 13and including the step of positioning said embossment as projectionsfrom an outer surface of the laminate which defines the interior of thecontainer.
 15. The method of claim 14 wherein said embossments projectfrom an outer surface of the laminate a distance not greater than thethickness of the top wall of the container.
 16. The method of claim 14wherein all layers of the laminate are retained intact.
 17. The methodof claim 14 wherein said weakened area exhibits a rupture resistanceless than the rupture resistance of the remainder of said embossments.18. The method of claim 17 wherein said weakened area exhibits a ruptureresistance mean value of about 4.7 lbf applied to said weakened area bymeans of a 4 mm diameter drinking straw.
 19. The method of claim 18wherein said straw is of a polymeric material.
 20. A blank comprising: asubstrate having a plurality of score lines, the substrate configured tobe folded along the plurality of score lines to form a sealed enclosure;a structurally weakened area being defined on a portion of thesubstrate, the structurally weakened area comprises a plurality ofembossments configured to be produced by a male die insert and a femaledie insert on opposed surfaces of the substrate, the structurallyweakened area includes a thickness that is substantially less than athickness of the substrate and wherein the structurally weakened area isconfigured to be ruptured upon applying a force thereto to permit accessto an interior region of the sealed enclosure.
 21. The blank of claim 20wherein the substrate further comprises an inner surface and an outersurface, an inner layer of a polymer coated on the inner surface of thesubstrate, an outer layer of a polymer coated on the outer surface ofthe substrate wherein the inner and outer layers are configured toresist a force of about 4.7 lbf applied to the structural weakening areaof the plurality of embossments.
 22. The blank of claim 20 wherein thesubstrate further comprises an inner surface layer of polymer coated onthe inner surface of the substrate and wherein the substrate isconfigured to resist a force of about 4.7 lbf applied to the structuralweakening area.
 23. The blank of claim 20 wherein the plurality ofembossments further comprises shallow indentation embossmentsintersecting one another in the structurally weakened area and eachshallow indentation embossments has a substantially semi-circularcross-sectional geometry.
 24. The blank of claim 20 wherein theembossments project inwardly of the substrate and into the plane of thesubstrate.